Tom Kha Gai (Thai Coconut Chicken Soup with Galangal and Lemongrass)

Tom kha gai (ต้มข่าไก่) is Thailand's coconut chicken soup: a gentle, milky broth scented with galangal, lemongrass and makrut lime leaves, sharpened with lime juice and fish sauce and finished with a handful of cilantro. It is the mellow cousin of tom yum, and when the evenings turn cool it is exactly the kind of bowl you want: warming from the galangal and chilies, soothing from the coconut, and ready faster than most weeknight soups.

Three things make this version work. First, the aromatics are simmered in stock before most of the coconut milk goes in, so the broth carries real galangal and lemongrass flavor instead of just floating slices. Second, the coconut milk is added late and never boiled hard, which keeps it smooth and white rather than split and grainy. Third, the lime juice goes in only after the heat is off, so the soup tastes bright and fresh instead of flat. Sliced chicken thigh stays tender in the light simmer, and straw or oyster mushrooms soak up the broth like little sponges.

Ingredients

• 500 g (1.1 lb) boneless, skinless chicken thighs, sliced into thin bite-size pieces
• 800 ml (two 14 oz cans) full-fat coconut milk
• 400 ml (1 2/3 cups) chicken stock
• 60 g (2 oz) fresh galangal, about a 6 cm (2 1/2-inch) piece, peeled and thinly sliced
• 2 stalks lemongrass, tough outer layers removed, bruised and cut into 5 cm (2-inch) pieces
• 6 makrut lime leaves, torn in half
• 2 shallots, peeled and halved
• 200 g (7 oz) straw mushrooms (one drained can) or oyster mushrooms, torn into bite-size pieces
• 100 g (3.5 oz) cherry tomatoes, halved (optional)
• 3 to 5 Thai bird's eye chilies, lightly bruised with the side of a knife
• 3 tablespoons fish sauce
• 1 tablespoon palm sugar or brown sugar
• 3 tablespoons fresh lime juice (about 1 1/2 limes)
• 1 small bunch cilantro, roughly chopped
• Cooked jasmine rice, to serve

Instructions

1. Prepare the aromatics. Peel the galangal with a spoon or paring knife and slice it into thin coins; it stays firm, so don't worry about slicing it paper thin. Peel the lemongrass down to the pale core, bruise it with the back of a knife and cut it into 5 cm pieces. Tear the lime leaves in half, discarding the center stem.
2. Pour the chicken stock into a pot with 200 ml (scant 1 cup) of the coconut milk, using the thinner liquid from the bottom of the cans. Add the galangal, lemongrass, lime leaves and shallots and bring to a gentle simmer over medium heat. Simmer for 5 minutes so the broth takes on the aroma.
3. Add the sliced chicken and stir to separate the pieces. Keep the heat at a gentle simmer and cook for 5 to 6 minutes, until the chicken is just opaque all the way through. Skim off any foam.
4. Add the mushrooms, chilies and tomatoes (if using) and simmer for 2 to 3 minutes more, until the mushrooms are heated through and the tomatoes have just softened.
5. Pour in the remaining coconut milk and turn the heat to low. Warm the soup for 3 to 4 minutes, until it is steaming and small bubbles just appear at the edge of the pot. Do not let it come to a rolling boil: coconut milk that boils hard separates into oil and grainy curds, and the soup loses its silky, white look.
6. Turn off the heat. Stir in the fish sauce and palm sugar until the sugar dissolves.
7. Add the lime juice off the heat and taste. The soup should be salty and sour in equal measure with just a hint of sweetness; add more fish sauce, lime juice or sugar a teaspoon at a time until it tastes right to you.
8. Ladle into bowls, making sure everyone gets chicken and mushrooms, and top with cilantro. Serve hot with jasmine rice. The galangal, lemongrass and lime leaves are left in for flavor but are not meant to be eaten.

Tips

• Galangal is what makes tom kha taste like tom kha, so look for it fresh or frozen at Asian grocers; dried slices work if soaked in warm water for 20 minutes. Ginger is only a last resort: use half the amount and add an extra squeeze of lime, and expect a warmer, less citrusy flavor.
• No straw mushrooms? Oyster, shiitake or button mushrooms all work. Chicken breast works too if you slice it thin and add it in step 3 for just 3 to 4 minutes; thigh is more forgiving.
• Use canned full-fat coconut milk with as few additives as possible. Light coconut milk makes a thin soup, and brands with lots of stabilizers taste flat. Keeping the thin liquid for step 2 and the thick cream for step 5 gives the best texture.
• For a touch of heat and color, stir a teaspoon of Thai chili jam (nam prik pao) into the finished soup, or add a spoonful of chili oil to each bowl.
• Leftovers keep in the fridge for up to 3 days. Reheat gently over low heat without boiling, and add a fresh squeeze of lime before serving. Freezing is not ideal because the coconut milk separates, but it will keep for 1 month if you whisk it well while reheating.
• Serve with jasmine rice and a simple stir-fry such as pad krapow or garlic morning glory (pad pak boong), or start a Thai meal with it alongside a green papaya salad.

Nutrition

Nutrition information is an estimate only: about 580 kcal, 28 g protein, 46 g fat, 14 g carbohydrate per serving, without rice.